From: Vasily Leonenko Date: Thu, 29 Jan 2026 18:12:49 +0000 (+0300) Subject: runtime: align end of systemstack_switch prologue on amd64 for consistency with gosav... X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=f14d8975a21e24aa33e0b496e822fdcb285879b9;p=gostls13.git runtime: align end of systemstack_switch prologue on amd64 for consistency with gosave_systemstack_switch gosave_systemstack_switch saves PC with fixed offset of 8 bytes from systemstack_switch to bypass prologue. This commit makes this offset consistent with actual address of UNDEF instruction intended to be at that address. Fixes #71440 Change-Id: Ibe6458c5bcb0bdaec228a2f13d6aec7ecc0e319e Reviewed-on: https://go-review.googlesource.com/c/go/+/740360 LUCI-TryBot-Result: Go LUCI Auto-Submit: Keith Randall Reviewed-by: Keith Randall Reviewed-by: Keith Randall Reviewed-by: Dmitri Shuralyov --- diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s index add69aa500..39219babcc 100644 --- a/src/runtime/asm_amd64.s +++ b/src/runtime/asm_amd64.s @@ -510,6 +510,8 @@ goodm: // The frame layout needs to match systemstack // so that it can pretend to be systemstack_switch. TEXT runtime·systemstack_switch(SB), NOSPLIT, $0-0 + // Align for consistency with offset used in gosave_systemstack_switch + PCALIGN $8 UNDEF // Make sure this function is not leaf, // so the frame is saved. @@ -885,8 +887,9 @@ TEXT ·publicationBarrier(SB),NOSPLIT,$0-0 // Smashes R9. TEXT gosave_systemstack_switch<>(SB),NOSPLIT|NOFRAME,$0 // Take systemstack_switch PC and add 8 bytes to skip - // the prologue. The final location does not matter - // as long as we are between the prologue and the epilogue. + // the prologue. Keep 8 bytes offset consistent with + // PCALIGN $8 in systemstack_swtich, pointing start of + // UNDEF instruction beyond prologue. MOVQ $runtime·systemstack_switch+8(SB), R9 MOVQ R9, (g_sched+gobuf_pc)(R14) LEAQ 8(SP), R9